INFLUENCE OF RHEOLOGY AND SURFACE-PROPERTIES IN THE ADHESION OF UNCROSS-LINKED PRESSURE-SENSITIVE ADHESIVES

We consider the adhesion of a pressure sensitive adhesive on different substrates (Pyrex, stainless steel, Plexiglas). First, we characteriz e the rheological properties of the adhesive material and compare it w ith the predictions of Lodge's model. Then we investigate the adhesive properties using a special machine which enables us to peel at 90 deg rees with a fixed peeling front and we construct peeling master curves on different substrates. The mechanisms of peeling are analyzed by lo oking at the peeling front using a video camera. We realize that the f low within the filaments and ribs observed is mainly of elongational t ype. Also, by looking at the shape of the backing, we find out that mo st of the energy is spent within the ribs or filaments. To understand the effect of rheology on adhesion, we propose a simple model to predi ct peeling curves, by assuming that the flow is mainly of elongational type. This explains the high energy regions. At low velocities, surfa ce energies become important and their effect is also analyzed. To con clude, we propose different dimensionless equations which explain the importance of the relevant parameters, via dimensionless numbers. Thus the peeling energy is investigated, as well as the condition which pr edicts the transition from cohesive to adhesive peeling.